Fan blade



April 15,1941. E. L R 2;238,749

FAN BLADE I Filed Jan. 30, 1939 2-5t BY (1%ENT9R M cM ATTORNEY.

Patented Apr. 15, 1941 UNITED STAT ES PATENTI' OFFICE James Poitier, Detroit, Mich., assignor to Clarence 8. Swift, doing business as Swift Manufacturing Company, Detroit, Mich.

Application January 30, 1939, Serial N0. 253,518 (Cl. 170-159) 4 Claims.

This invention relates to fans and more particularly to fan blades.

One of the objects of the present invention is to provide an improved fan which delivers more ically and does not materially set up in operation vibrations in the supporting structure.

It is an added object of the present invention to provide an improvedstructure of the foregoing character which is simple in construction, dependable in operation and is relatively inexpensive to manufacture.

Other objects of this invention will appear in the following description and appended claims.

reference being had to the accompanying drawing forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a front view of a present invention.

Fig. 2 is a side view of the fan shown in Fig. 1, looking from the right-hand side thereof.

Fig. 8 is a sectional view taken in the direction of the arrows on the section plane passing through the line 3-3 of Fig. -1.

Pig. 4 is a sectional view. taken in the direction of the arrows on the section plane passing throughthelineH of Fig. 1.

' Fig. 5 is a front view illustrating a modified construction oi a fan embodying the present invention. g

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawin since the invention ever, that my invention is equally applicable to the fans having other numbers oi blades, as well as to different types of fans or propellers.

,. Referring to Figs. 1 to 4 inclusive, the structure illustrated therein comprises two elongated members indicated generally by numerals I. and II, said members being arranged in crossed relation and secured together at their middle portions in any suitable'manner, such as by means of rivets l2, to form a boss or hub l3. Reinforcing ribs l4 and I] are stamped in the members in such a way that each individual reinforcing rib is formed fully on one member and partly on the other member. Such a construction increases the strength of the fan particularly at the roots of the individual blades where the bending moment is greatest, and provides for better interlocking of .members II and H. i 7

fan embodying the On the ends of the members l0 and ii there are formed fan blades, each of the two blades formed on the member It being designated by numeral I, while each of the two blades formed on the member II is designated by numeral l'l. All of the blades are twisted around their longitudinal axes, as is best shown in Fig. 2, to produce the desired pitch angle, said angle, in the present instance, being equal for all four blades. Each of the blades so formed has a leading edge Ito or Ila respectively, a trailing edge lib or "b respectively, and a tip or toe lie or "c respectively. A central aperture II and a plurality of or roaring noises, the elimination. of which has proved to be extremely diflicultc In accordance with the present invention, means are provided eliminating said noises and producing a smoothly and quietly running fan or propeller.

0n the trailing edges lib of the blades 18 there are provided a plurality of irregularities, in the present instance, corrugations II formed on the blades, which irregularities make the blades II and H not quite identical in their shape. By virture of such a construction a much quieter fan is produced. It is my present theory that the invention. The constructions shown are fans of the four-blade type. It will be understood, howmore quiet operation 'of my improved fan results from the fact that the rhythmic a'ir waves produced by the blades ll and I! are difierentin pitch and character and, therefore, of adding together as is the case in identical blades of conventional fans, the waves produced by the blades of my improved fan' are of different pitch and character and, therefore, they interfere and break each other, producing irregular air motions which do not travel far. I

In accordance with the inventiompractically any means which produce unequal blades or blades 01 qiflerent shapes capable of producing unequal or interfering air vibrations, waves'or impulses may be utilized to produce the beneficial results contemplated by the present invention. For instance, the blades may be of diflerent widths and lengths. The radii of the curvatures at the blade tips may be difl'erent. corrugations of different kinds and sizes may be provided on adjacent blades. Reinforcing ribs may be of different sizes thereby producing blades 01' different stiil'nesses and, consequently, ofldifferent vialso be noted that the uneven blades are arranged adjacent each other and, therefore, the rhythmic alibeats produced by the blade I! are deadened by the beats produced by the blade II which follows in operation immediately after the blade i'l'. It is desirable to arrange blades in such a way that blades of identical character are disposedion the same diameter or on a line passing through the center of the tan hub in orde to produce balanced fans. Fig. 5 illustrates a modified structure constructed in accordance with the above disclosures. In saidstructure the blades 25 are somewhat longer than the blades 26 and the' radii oi. curvature at their tips 250 are somewhat larger than at the tips 260. corrugations ii of each of the blades 25, are flner than the single corrugation II of each of the shorter blades 26.

aeeavee 2. In a fan, a plurality of stamped sheet metal members arranged one across the other and securedtogether, a blade formed on each end of each of said members to provide an even plurality of blades, each of said blades having' a leading and a trailing edge, and corrugations on the trailing edges of only half of sald blades, the blades with corrugations and the blades without the same being arranged alternatively, thereby causing adjacent blades to set up in operation air waves of mutually interfering frequencies.

3. In a tan, two elongated stamped sheet metal members arranged crosswise and secured together at their middle portions; a blade formed on each end of each of said members to provide four radiating blades, each of said blades having a leading edge, a trailing edge and a tip, and stamped corrugations on the trailing edges of the two blades formed on one 01' said members, said corrugations serving to break up the rhythm of the sound waves produced by the blades.

4. In a fan, two elongated stamped sheet metal members arranged crosswise and secured together at their middle portions; a blade formed on each end of each of said members to provide four radiating blades, each of said blades having a being of different formation in order to set up in operation mutually interfering and deadening sound waves.

JAm E. PEL'I'IER. 

